| No | Pattern | Freq | Relations |
|---|---|---|---|
| 1 | must be [vb pp] [adv] [to-vb] | 30 |
|
| 2 | must be [vb pp] [adv] [to-vb] | 30 |
|
| 3 | must [be] [vb pp] [adv] [to-vb] | 30 |
|
